1. Field of the Invention
The present invention relates to a watch case, equipped at its circumference with a decoration piece that extends around a middle part of the case to which are connected a back cover and a glass plate, an inner surface of the middle part surrounding a clockwork movement supported by a circular piece and connected to a crown through an arbor.
2. Description of the Prior Art
The problem associated with the manufacture of watches of this type where the decoration piece is present for esthetic reasons only, is based on the incompatibility of the manufacturing precision figures when the decoration piece is made from a very hard and only low resilient material such as glass, crystal glass or precious or semi-precious stones; this problem is well known to watchmakers. In fact, whereas the cases are manufactured with a precision in the order of 0.01 mm, this precision cannot be respected with the above-mentioned hard materials where internal tensions are present which may lead to fissures and fractures of the machined material. The manufacturers cannot generally offer a better precision than about 0.1 mm, considerable deviations of the dimensions of different pieces which are successively manufactures being further unavoidable.
It is therefore highly desired to compensate the allowances described above.
Efforts have already been made to solve the problem. Thus, Swiss patent specification No. CH-A-654,167 discloses a watch case comprising an annular piece 7 made from a material whose machining is very difficult. However, the proposed means do really not bring about a solution of the above-depicted problem since certain portions of said piece must still be machined in order to respect precise dimensions (page 4, left column, lines 19 ff.). Now, it is just this type of machining which should be made superfluous by the present invention.
European patent No. EP-B1-0,150,746 also describes a watch case comprising a middle portion formed by two concentric rings, namely an inner ring which constitutes the very middle portion of the watch case, surrounding the clock movement, and an outer ring (or annular piece or decoration piece) exerting before all a decorating function. However, this piece, maintained between a bottom and a frontal plate (covering the inner ring on which it is cemented), must have essentially the same thickness as the inner ring. In fact, it is stated that, should the decoration piece be separated from the middle of the case by a seal, it is axially retained by the clamping force between the bottom and the frontal plate only, no other fastening means being provided. This solution is therefore not satisfactory since the thickness of the decoration piece must necessarily be machined in respecting, here again, precise dimensions. If, on one hand, the thickness of the outer decoration ring is higher than the required dimension value, the bottom cannot be correctly fastened against the middle portion (the inner ring), which will lead in a mostly undesired manner to a very rapid breakdown of the watch since neither the tightness nor the dampening of shocks are assured any longer; moreover, the decoration piece will be damaged during the mounting of said bottom on the middle portion. If, on the other hand, the thickness of that outer ring is lower than the required dimension value, it will begin to move in axial direction, and this movement will damage the ring with time, together with the undesired unaesthetic effect caused by a not wanted liberty movement.
Furthermore, the problems caused by the differences between the dilatation coefficients of the metal forming the middle portion of the case and the material from which the decoration piece is made, are even not dealt with and still less resolved.
The purpose of this invention is to overcome the above-discussed disadvantages. This purpose is fulfilled by a watch case of the above-indicated kind wherein clearances are provided between the decoration piece and the middle of the case and the bottom, respectively, in such a manner that said decoration piece is out of contact with the middle and with the bottom, and wherein means are provided and established in order to maintain said clearances.
Further features, advantages and special realizations of the invention will become evident from the following description and from the dependent claims whose contents are incorporated by reference into this specification.
The implementation of the means according to the invention is particularly advantageous not only because the drawbacks associated with the watch cases of the prior art are overcome, but also because the proposed present solution is remarkably simple, elegant and cheap. Moreover, the same means fulfill simultaneously and in an ideal fashion the functions of tightness and shock absorption. These means allow to realize the ideal synthesis always searched for, namely manufacturing costs reduced to a minimum, functioning reliability in all situations, selected esthetics and possible or polyvalent presentation variations.
A special embodiment of the invention will now be described in detail as a non-limiting example thereof, and reference is made to the attached drawing.